1. Field of the Invention
The invention generally relates to alternative energy sources and fuels. More specifically, the invention relates to methods for multimedia evaluation of butanol-containing fuels, including comparing such fuels to an ethanol-containing fuel standard.
2. Background of the Invention
Global demand for liquid transportation fuel is projected to strain the ability to meet certain environmentally driven goals, for example, the conservation of oil reserves. Such demand has driven the development of technology which allows utilization of renewable resources to mitigate the depletion of oil reserves. This invention addresses the need for improved alternative fuel compositions and processes which allow for the conservation of oil reserves. Such compositions and processes would satisfy both fuel demands and environmental concerns.
Ethanol is routinely blended with both finished gasoline and gasoline subgrades (e.g., blendstocks for oxygenate blending) to make fuel blends. Butanol is an important industrial chemical that is also suitable for use in fuel blends. Butanol may be made through chemical synthesis or by fermentation. Recombinant microbial production hosts, expressing a 1-butanol biosynthetic pathway (Donaldson et al., U.S. Appl. Pub. No. 2008/0182308), a 2-butanol biosynthetic pathway (Donaldson et al., U.S. Appl. Pub. Nos. 2007/0259410 and 2007/0292927), and an isobutanol biosynthetic pathway (Maggio-Hall et al., U.S. Appl. Pub. No. 2007/0092957) have been described.
The use of butanol in fuel blends has several advantages over the use of ethanol. For example, because butanol has energy content closer to that of gasoline, consumers face less of a compromise on fuel economy by using a butanol-containing fuel. Butanol is also advantageous because it yields only CO2 and little or no SOX or NOX when burned in the standard internal combustion engine, and is less corrosive than ethanol. Also, butanol has a lower vapor pressure than ethanol, meaning that it can be easily added to conventional gasoline and does not require automakers to compromise on performance to meet environmental regulations. Butanol has a blending Reid vapor pressure (RVP) of 5.1 psia, which is considerably lower than that of ethanol (blending RVP of 19 psia). As a result, butanol offers enhanced value to refiners who are typically RVP-constrained during summer blending season. The lower vapor pressure of butanol also means that it can be used in higher blend concentrations than ethanol without requiring especially adapted vehicles.
In addition, butanol fuel blends are less susceptible to separation in the presence of water than ethanol fuel blends. Furthermore, butanol's chemical properties also allow it to be blended at least 16% by volume in gasoline, thereby displacing more gasoline per gallon of fuel consumed than the standard 10% by volume ethanol blend. The water-solubility and corrosivity of butanol is also sufficiently low such that butanol-containing fuels can be transported in existing pipelines without risk of phase separation.
Butanol-containing fuels with up to 3.7 wt % oxygen (approximately 16 vol % of butanol) and meeting certain additional requirements have been approved by the U.S. Environmental Protection Agency as substantially similar to baseline gasoline under terms of the Octamix Waiver issued under §211(f) of the Clean Air Act Amendments [53 FR 3636 (2/8/88)]. However, there is a need to further determine the automotive performance parameters of such butanol-containing fuels.
Ethanol-containing fuels can have a detrimental effect on automotive materials and components. Pierce et al., “Effects of Fuel Exposure on Physical Properties of Selected Plastics,” SAE International, International Congress and Exposition (1990); Shiotani et al., “Research About Applicability of Biomass Ethanol for Motor Fuel,” Society of Automotive Engineers of Japan, Academic Lecture Meeting, May 20, 2005. However, only limited information about the effects of butanol-containing fuels on automotive materials and components is available.